An electrically erasable programmable read only memory (EEPROM) is a memory device that is used in many applications where limited amounts of non-volatile storage is needed. They can be found in many applications such as analog/digital television, set-top boxes, video equipment, games, audio systems, programmable controllers in a manufacturing setting, printers, graphics cards, and computer motherboards, to name a few.
In actuality, EEPROMs are not strictly read only memory, but are actually a hybrid between read only memory (ROM) and random access memory (RAM), since they can be programmed, erased, and reprogrammed. Other types of memory are ROM, which were originally hardwired devices with preprogrammed data. Programmable ROM (PROM) was the next advancement in that the devices were purchased unprogrammed, but could be programmed utilizing a device programmer. The device programmer would write data to the PROM, but the devices would not be erasable. Once PROMs were written, they would have to be discarded if the data needed to be changed.
EPROMs eliminated this problem in that they can be programmed and erased multiple times. However, to erase the data, the device must be removed and exposed to an intense ultraviolet (UV) light, which would restore the device to its original unprogrammed state.
EEPROMs are programmable and erasable like EPROMS, but are erased electrically. EEPROMS have continued to replace UV EPROMS in many applications as they do not require UV light or need to be removed from the system to be erased. EEPROMS are erased electrically by applying an electric field at the floating gate in the cell. EEPROMS can be erased on an individual byte basis in comparison to flash EPROMS, which must be erased by array or sector.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with the present invention as set forth in the remainder of the present application with reference to the drawings.